Although visual perception may seem to be a unitary process subjectively, it is likely that various systems in the brain analyze different aspects of the visual environment. Morphologically differentiated areas of the retina may subserve different modes of visual analysis. Because of the confounding of head movements with eye-in-head movements, it is technically very difficult to measure how freely moving subjects - human or animal - use the parts of their visual fields that correspond to these differentiated retinal regions. The dove may make a good animal model to use in visual field research since unrestricted animals tend to use head movements rather than oculomotor movements to visually scan their environments. Doves are also attractive as experimental animals since their visual anatomy is well understood and many of the homologous mammalian structures have been identified. In pilot work, I have demonstrated that doves tend to use different regions of their retinae in different behavioral situations. In this application an experiment is proposed to establish whether this selective use of parts of the bird's visual field is merely due to the refractive state of these regions or if it is due to neurological factors biasing the use of different retinal regions for different response modes. A computer-based video process for the real time analysis of object movement will be developed in the course of this research.